In recent years, portable information devices such as PDAs (Personal Digital Assistants) and notebook computers have come into widespread use. Such portable information devices store multiple information such as information on the individual using the portable information device and information on the company to which the individual belongs.
Therefore, in cases where such portable information devices are transferred to a third party as a result of being lost, mislaid, or stolen, it is undesirable for the third party to know the stored information and the demand for preventing such an occurrence is strong.
Further, as in the case of keyless entry for an automobile, when a door lock is locked or canceled wirelessly by using radio waves instead of using a key, the user carries a portable apparatus that is equivalent to an automobile key and operates the locking or unlocking of the automobile door lock remotely by means of a wireless signal by using the portable apparatus.
In the case of such a keyless entry system, when a door is locked or unlocked easily by means of a portable apparatus or the like owned by a third party, it is undesirable for the third party to assume ownership of the automobile or easily steal or commit mischief with the vehicle and so forth.
Hence, in cases where an automobile door lock apparatus or other apparatus is operated wirelessly, there is a requirement to prevent takeover of ownership or illegal operation and to render the security reliable.
Such takeover of ownership and illegal operation are not limited to an automobile door lock and, in addition to the above PDA (Personal Digital Assistant) and notebook computers, there is a requirement to similarly prevent takeover of ownership and illegal operation for portable apparatuses that remotely monitor and operate devices such as house door locks and camera and so forth. Therefore, there is similarly a need for reliable security in cases where such devices are remotely monitored and operated and so forth wirelessly.
On the other hand, memory cards (memory stick, SD memory cards (registered trademark) and multimedia cards and so forth) that can be optionally inserted in portable apparatuses have become widespread in recent years and portable apparatuses that allow such cards to be inserted have also started to become widespread.
By providing such a memory card with a function serving to render the security reliable, it is thought that the user will be able to obtain highly accurate security simply by using a cellular phone or the like that he or she already owns.